de4py is a Python reverse-engineering toolkit focused on deobfuscation and malware analysis. It provides a dual-interface (PySide6 GUI and TUI CLI) with a modular multi-engine architecture. The core 'onyx' engine performs AST-based deobfuscation through a pipeline of stages: string decoding, constant folding, control-flow deobfuscation, proxy cleaning, VM devirtualization (both switch-dispatch and table-dispatch register VMs), and AI-assisted renaming via local or cloud LLMs. Legacy obfuscators (Jawbreaker, BlankOBF, PlusOBF, etc.) are handled by separate detectors. Additional features include a PyInstaller/unpy2exe analyzer, live process injection and monitoring (PyShell with native C++ DLLs), online/offline .pyc decompilation via PyLingual, behavior monitoring (file/process/network/SSL hooks), an extensible plugin system (themes and deobfuscators), and a comprehensive localization framework (18+ languages). A built-in self-updater with checksum verification and DevTools (widget inspector, performance metrics, scenario engine) indicate a mature, production-oriented application. The codebase balances advanced static analysis algorithms with polished UX, though some platform-specific dependencies (Windows DLLs, hardcoded paths) and a CC BY-NC 4.0 license limit broad reuse.